属性“RepositionMode”不是元素“ModalPopupExtender”的有效属性

Question

我的代码：        <ajaxToolkit:ModalPopupExtender ID="ModalPopupExtender1" runat="server"
                                        TargetControlID="btnChangeStyle"
                                        PopupControlID="panModalPopup"
                                        BackgroundCssClass="cssModalBackground"
                                        DropShadow="true"
                                        OkControlID="btnOK"
                                        OnOkScript="changeStyle()"
                                        RepositionMode="RepositionOnWindowResize"
                                        CancelControlID="btnCancel" 
                                        >
        </ajaxToolkit:ModalPopupExtender>
报错：属性“RepositionMode”不是元素“ModalPopupExtender”的有效属性

Answer 1

有人告诉我为什么？我查阅资料了解ajaxToolkit:ModalPopupExtender有这个属性的。http://msdn.microsoft.com/zh-tw/magazine/cc164247.aspx